WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 7Citation - Scopus: 7Investigating the Effects of Pa66 Electrospun Nanofibers Layered Within an Adhesive Composite Joint Fabricated Under Autoclave Curing(American Chemical Society, 2023) Esenoğlu, Gözde; Tanoğlu, Metin; Barışık, Murat; İplikçi, Hande; Yeke, Melisa; Nuhoğlu, Kaan; Türkdoğan, Ceren; Martin, Seçkin; Aktaş, Engin; Dehneliler, Serkan; Gürbüz, Ahmet Ayberk; İriş, Mehmet ErdemEnhancing the performance of adhesively joined composite components is crucial for various industrial applications. In this study, polyamide 66 (PA66) nanofibers produced by electrospinning were coated on unidirectional carbon/epoxy prepregs to increase the bond strength of the composites. Carbon/epoxy prepregs with/without PA66 nanofiber coating on the bonding region were fabricated using the autoclave, which is often used in the aerospace industry. The single lap shear Charpy impact energy and Mode-I fracture toughness tests were employed to examine the effects of PA66 nanofibers on the mechanical properties of the joint region. Scanning electron microscopy (SEM) was used to investigate the nanofiber morphology and fracture modes. The thermal characteristics of Polyamide 66 nanofibers were explored by using differential scanning calorimetry (DSC). We observed that the electrospun PA66 nanofiber coating on the prepreg surfaces substantially improves the joint strength. Results revealed that the single lap shear and Charpy impact strength values of the composite joint are increased by about 79 and 24%, respectively, by coating PA66 nanofibers onto the joining region. The results also showed that by coating PA66 nanofibers, the Mode-I fracture toughness value was improved by about 107% while the glass transition temperature remained constant.Article Citation - WoS: 9Citation - Scopus: 13Analysis of Adhesively Bonded Joints of Laser Surface Treated Composite Primary Components of Aircraft Structures(Elsevier, 2023) Martin, Seçkin; Nuhoğlu, Kaan; Aktaş, Engin; Tanoğlu, Metin; İplikçi, Hande; Barışık, Murat; Yeke, Melisa; Türkdoğan, Ceren; Esenoğlu, Gözde; Dehneliler, SerkanThe performance of the adhesively bonded aerospace structures highly depends on the adhesion strength between the adhesive and adherents, which is affected by, in particular, the condition of the bonding surface. Among the various surface treatment methods, as state of the art, laser surface treatment is a suitable option for the CFRP composite structures to enhance the adhesion performance, adjusting the roughness and surface free energy with relatively minimizing the damage to the fibers. The aim of this study is the validation and evaluation of the adhesive bonding behavior of the laser surface-treated CFRP composite structures, using the finite element technique to perform a conservative prediction of the failure load and damage growth. Such objectives were achieved by executing both experimental and numerical analyses of the secondary bonded CFRP parts using a structural adhesive. In this regard, to complement physical experiments by means of numerical simulation, macro-scale 3D FEA of adhesively bonded Single Lap Joint and Skin-Spar Joint specimens has been developed employing the Cohesive Zone Model (CZM) technique in order to simulate bonding behavior in composite structures especially skin-spar relation in the aircraft wing-box.Article Citation - WoS: 4Citation - Scopus: 4Seismic Vulnerability Assessment of an Unanchored Circular Storage Tank Against Elephant's Foot Buckling(Springer, 2022) Bektaş, Nurullah; Aktaş, EnginPurpose Seismic vulnerability assessment of liquid containing storage tanks is the most vital relevance for industrial plants and society safety to endure damage during impending earthquakes. Because such systems also play an essential role in the public lifeline and also ensure continued use in emergencies. Furthermore, considering that the material contained in individual plants could be hazardous, requisite precautions have paramount importance against undesired leakage. The high internal pressure and axial forces exerted by the liquid in the steel tanks near the tank wall bottom produce elastic-plastic buckling, also known as Elephant's Foot Buckling (EFB). As far as the authors are aware, no study has been carried out that involves a critical assessment and comparison of IDA and truncated IDA-based EFB failure criterion. This study provides insight into incremental dynamic analysis (IDA) and truncated IDA-based seismic evaluation of cylindrical unanchored steel storage tanks by employing a developed pressure-based surrogate modeling approach. For this purpose, probability-based seismic assessment of a representative sample is considered based on IDA and truncated IDA approaches to identify the potential of the EFB failure and to explore potential enhancements in the sophisticated structural analysis model to prevent the hazardous effects of impending earthquakes. Methods Due to the significance of industrial plants for public safety and benefit, the structural response evaluation methods for different types of storage tanks have been widely reported. In the literature, the most comprehensive analytical assessment methodology is the IDA approach, in which nonlinear time-history analyses are considered in the finite element analysis model to assess the structural model's seismic performance. Results To generate fragility curves, both IDA approaches are employed, taking into consideration and ignoring uncertainty of material properties. The values of the two methods-based fragility curves approach each other as the magnitude of dispersion increases. Conclusion The two fragility curves give the probability of failures close to each other as the dispersion amount increases while considering the uncertainty of the material properties. In addition, fragility curves generated based on the truncated IDA have been found to give a higher probability of failure, up to 32.5 percent. When compared to the IDA-based fragility curves, the truncated IDA-based fragility curves were found to be on the conservative side.Article Citation - WoS: 11Citation - Scopus: 12A Novel Transformable Structural Mechanism for Doubly Ruled Hypar Surfaces(The American Society of Mechanical Engineers(ASME), 2015) Maden, Feray; Aktaş, Engin; Korkmaz, KorayA novel structural mechanism (SM) that is capable of transforming itself into various hyperbolic paraboloid (hypar) geometries is introduced in this paper. Composed of straight bars and novel joint types, the SM is designed based on the ruled surface generation method. Thus, the paper first investigates the geometrical properties and morphology of the hypar surface. Second, it constructs the SM and discusses its transformation capability with respect to its kinematic properties. Then, it presents a parametric model not only to analyze the geometry and possible configurations of the SM but also to prepare a model for the structural analysis. Finally, a transformable shelter structure is proposed as an architectural application of the SM and its feasibility is tested based on the structural analysis conducted in different configurations of the structure. According to the results of the structural analysis, the strength, and the stiffness of the structure are discussed in detail.Article Citation - WoS: 1Citation - Scopus: 2Consolidation of a Bath Ruin in an Archaeological Site(Taylor and Francis Ltd., 2022) Durmuşlar, Feyza; Turan, Mine; Yücetürk, Kutay; Aktaş, EnginThe study has focused on consolidation of a historical bath ruin in an archaeological site. Cevher Pasa Bath, which is located in Tabae archaeological site in Denizli, Turkey and dated to the 15th century, presents structural problems. The aim of the study is to propose a framework for planning consolidation of the ruins of Cevher Pasa Bath so that conservation work regarding similar masonry ruins in archaeological sites can be guided. Thus, methods of architectural restoration and civil engineering are combined in an interdisciplinary scope. Provision of temporary shoring as an emergency intervention, consolidation and presentation of the ruin within the scope of an interdisciplinary restoration project, and monitoring of the asset within the frame of a monument management plan are suggested, respectively. Structural analysis considering stress and overturning moment checks are performed. Consolidation work includes only supporting of arch remains. Some walls of the ruin are weaker than other parts. These parts need further detailed analysis, and if necessary, further consolidation and strengthening are to be carried out. The monument management plan points out the necessity of collaboration of local and central administrations, and also non-governmental organisations.Article Citation - WoS: 9Citation - Scopus: 12Structural Analyses and Assessment of Historical Kamanlı Mosque in Izmir, Turkey(American Society of Civil Engineers (ASCE), 2010) Teomete, Egemen; Aktaş, EnginHistorical structures are one of the most precious pieces of cultural accumulation. In this study, an interdisciplinary work was conducted to assess the structural condition of a historical masonry structure, Urla Kamanl Mosque in zmir, Turkey. The structure is a member of group of structures, Yahi Bey Complex, which includes a Turkish bath, a tomb, two fountains, and a primary school. The structure dates back to early 14th century to mid-15th century. History investigation, measurement survey, long-term settlement, and moisture observations were conducted. Nondestructive and destructive material tests were performed on stone, brick, and mortar. 3D finite-element model of the structure was used to investigate the critical locations of the structure under its self-weight, seismic load, and settlement load. Linear elastic and nonlinear settlement analyses were conducted to investigate the reason for massive cracks challenging the structural integrity. © 2010 ASCE.